I've got a friend still with the old-style green card. I think it is free, I'll ask him next time I see him, but it may only be available to those who already have it, if you see what I mean.
Re upgrading from Gold to Platinum - you need to have closed your membership reward account first, before you apply for the Platinum, to qualify for the MR bonus.
Also there is a referral offer on at the moment, so that you can get 42,000 MR points if you take out a Platinum card, with the referrer getting 22,000. There are plenty of people on here willing to refer you, me included. Feel free to ask if you would like a referral.
As to whether it is worthwhile, I'd say it depends on whether you and your family would make use of the insurance benefits, now that they have reduced. Whilst it is annoying, it makes little difference to me as I can if I wish pay for travel using the Platinum card, not being a business traveller. If you have under aged 70 parents who travel, it's still a bargain, as long as you are happy for them to use the card and reimburse you (think of the hassle v the extra MR points!). I think I will continue to shuffle the card backwards and forwards, with hubby referring me near the end of his membership year and then not renewing his card and vv, as long as there continues to be bonus MRs for doing so. If that continues, it makes it 64,000 MR points + £300 per annum, which I am more than happy with (though I'd be even more happy if US Airways were a partner!).